I worked at ASEM English center in Vinh, Vietnam, through API, in 2016. I and the 6 other teachers I lived with, some of whom were university students and some of whom were independent clients, expressed some very serious concerns about our safety and about the mistreatment of both Vietnamese and foreign employees at the site that API has refused to address and that continue unmitigated as of 2018. API has never sent a represnetative to visit the site or to meet your employers. They have no knowledge of conditions at the site and know very little about the city more generally. After you pay them and arrive in Vietnam, they will not help you.
I cannot emphasize this enough: there are many, many English centers in Vinh and throughout Vietnam, and you do not need to pay API or any other third party to be able to work at them.